Ultrafast Transmission Electron Microscopy—Instrumental Developments and Applications

Time-resolved variants of transmission electron microscopy have started to provide an unparalleled view into the fast and ultrafast dynamics of solid-state nanostructures. A crucial instrumental pre-requisite for constructing the next generation of time-resolved electron microscopes is the development of novel pulsed electron sources, fast detectors and versatile sample excitation schemes. In the first part of the talk, I will summarize our recent developments and characterization of a laser-driven cold-field emitter source (in collaboration with JEOL Ltd.), including the achieved electron pulse duration, spectral width, and electron beam brightness. Applications of these high-brightness electron pulses for the imaging of wavelength-dependent optical near-fields in transition metal dichalcogenides will be presented [1].<br/><br/>In the second part, I will focus on the application of event-based TimePix3 electron detectors in fast electron imaging. Using a neural network approach trained by experimental data with synchronized femtosecond electron pulses, we can improve the time-resolution of the TimePix3 detector utilizing the intrinsic correlations within event clusters [2]. Finally, as two applications for event-based electron imaging, I will discuss the excitation and phase-resolved mapping of nonlinear Duffing modes in a silicon membrane, demonstrating quality factors exceeding 10⁵, and the time-resolved Lorentz imaging of photoinduced charging in metal nanoparticles [3].<br/><br/>References<br/>[1] N. Müller, S. el Kabil, G. Vosse, L. Hansen, Chr. Rathje, S. Schäfer, arXiv.2405.12017 (2024)<br/>[2] J. Weber, S. Schäfer, Nano Letters 24, 5746 (2024).<br/>[3] A. Schröder, Chr. Rathje, L. van Velzen, M. Kelder, S. Schäfer, Ultramicroscopy 256, 113881 (2024).